In manufacturing a semiconductor integrated circuit, an object to be processed such as a semiconductor wafer is generally, repeatedly subjected to various single-wafer processes, such as a film deposition process, etching process, heat process, modification process, and crystallization process, so as to form a desired integrated circuit. In order to perform these processes, a process gas fit for the kind of process in question is supplied into a processing vessel. In a film deposition process, a source gas and a supporting gas, such as an oxidation gas and a reduction gas, are supplied into a processing vessel capable of forming a vacuum, from a showerhead disposed on a top part of the processing vessel. Thus, a film is deposited on a surface of a semiconductor wafer or the like heated in the processing vessel (JP 10-321613A).
If a source gas with a relatively low steam pressure and a relatively high activation energy is mixed with a supporting gas while the source gas is being fed, a film deposition reaction undesirably occurs. Thus, in order to prevent this reaction, there has been employed a jetting system in which the source gas does not contact the supporting gas until the source gas is jetted into the processing vessel from the showerhead. This jetting system is referred to as a “post-mix type”. In the post-mix type, the source gas and the supporting gas flow through separate channels in the showerhead, such that the gases are not mixed with each other. Due to this structure, deposition of an unwanted film, which results in formation of particles or the like, is prevented in the showerhead, and a required film can be mainly deposited only on a wafer surface.
However, in the course of repeatedly performing a film deposition process on the wafer, there has been a case in which an unwanted film ranging from several millimeters to several centimeters in diameter is deposited around source-gas jetting orifices, which are formed in a gas jetting surface of the showerhead facing the processing vessel. If such an unwanted film adhered to the gas jetting surface is left as it is, the film is peeled off from the gas jetting surface, thus causing formation of particles. Thus, it has been necessary to frequently carry out a cleaning process for removing the unwanted film. In this case, when it is possible to perform a so-called dry cleaning process that removes the unwanted film by passing a cleaning gas through the showerhead without detaching the same, only few problems arise. However, when an organic metal material gas containing certain kinds of high melting point metals, such as Hf (hafnium), is used as a material, there exists no effective cleaning gas. Thus, it is necessary to perform a so-called wet cleaning process that cleans the showerhead, while it is detached from a film-deposition apparatus body, by means of a cleaning solution. This is disadvantageous in that a lot of time is needed for a maintenance operation.